Coded track circuit signaling



Nov. 25, 1947. N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM original Filed Aug. 19, 1942 11 sheets-sheet 2 INVENTOR .Edu

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Ressued Nov. 25, 1947 CODED TRACK CIRCUIT SIGNALING SYSTEM Neil D. Preston, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Original No. 2,342,489, dated February 22, 1944,

Serial No. 455,328, August 19, 1942. Application for reissue April Z, 1947, Serial No. 738,767

` This invention relates to coded track circuit signaling systems for railroads, and more particularly to a centralized traiiic contr-o1 (C. T. C.) system for single track railroads.

In connection with the application of the conventional coded track circuit to single track railroads or like stretches of track having signals governing train movement in both directions, the direction in which the coded pulses are transmitted over the track rails of various track circuits for governing the indications of the associated signals has to be selected or governed to conform with the direction of train movement desired; and one method of determining the desired direction of track circuit coding, as disclosed, for example, in my prior application, Ser. No. 439,520, iiled April 18, 1942, now Patent No. 2,357,- 546 dated Sept. 5, 1944, is by the supervisory manual control of the C. T. C. system used for controlling the clearing of the signals and also if desired for governing the power operation of track switches. In certain respects the present invention is in the nature of a variation or modification of this prior disclosure; and itis not intended to make any claim herein to subject matter disclosed in said prior application.

The primary object of the present invention may be said to be the provision of a simple organization of coded track circuits in combination with a C. T. C. system, preferably of the code type, which will afford all the desired safety and facility for train movement on single track railroads, or for like stretches cf track having trame in both directions, the essential functions being performed without the use of line wires except as may be required for the transmission of controls and indications between a control olice and various eld locations over the C. T. C. system.

Generally speaking, and without attempting to denne the nature and scope of this invention, and considering one embodiment of the invention in its application to a typical single track railroad having passing sidings, it is pro-posed to employ the same manual controls of the C. T. C. system which are used to control the clearing of the signals governing train movement into and out of the stretches of single track for determining the direction of coding in the several track `sections, leaving the coding of these track sections in the direction corresponding with the last train movement, and providing for the automatic reversal of such existing direction of track circuit coding Whenever desired for opposing train movements by merely initiating coding operation of the track circuits in the opposite direction to 53 Claims. (Cl. 246-3) -back-up movement is to be made.

overpower and discontinue coding in the existing direction. For example, after a train has travelled through a stretch of single track between the ends of passing sidings in one direction, and has left the track circuits of the stretch coding in a direction for following train movements, amanual control for clearing the opposing starting or head-block signal, when exercised over the C. T. C. system, also acts to initiate track circuit coding at the opposite end of the stretch, which overcomes or bucks down, so to speak, the track circuit coding in the existing direction in the track circuits of the stretch in turn, thereby causing clearing of the head-block signal and intermediate signals for the new desired direction of train movement.

Considering more specifically the means employed, there is a code sending means for each end of the stretch of a single track between the ends of passing sidings Which once set into operation continues in operation until restored by code pulses received over the track rails from the opposite end; and when a manual control is exercised over the C. T. C. system to clear the headblock signal at one end of the stretch, operation of the code sending means for the opposite end of the stretch is also initiated, thereby applying driven code pulses to the track rails at that opposite end which act to overcome any existing coding of the track circuits in a coniiicting direction and thus cause clearing of the headblock signal and associated intermediate signals as required for the desired direction of train movement.

Among other things, this method of determining the direction of track circuit coding by overpowering any existing track circuit code in a conilicting direction, in the manner characterizing this invention, permits manual control of the clearing of an intermediate signal in a stretch of single track when desired to allow a train in this stretch to make a back-up move with safety, the coding of the track circuits in this instance being set up by the manual control for clearing the corresponding entering signal governing train movement out of the stretch at the end to which Similarly, in the case of an outlying switch in the single track stretch, the desired intermediate signals may be cleared under supervisory manual control to enable a train to move from this switch towards either end of the stretch, the coding of the track circuits in this case also being set up by a manual control to clear the corresponding entering ,Signlr sidings.

ktrol in a'different-- manner the direction yof track circuit coding for the siding sections constituting the stretches of main track opposite the passing.- Generally speaking, when, a. manual. control to clear the entering signal at eithersef-lY lected end of a siding section is exercised over the C. T. C. system, the desiredidirectionfof. ccd1-. ing in this section is set up-by` acting upon the. coded track circuit equipment at the same end of the siding section, rather than at theopposite end as in the case of the stretchvof sing-,lle trackbetween the ends of passing sidings;` Int-he;par;y ticular arrangement shown, the track circuit of the siding section is normally left coding ina predetermined prevailing direction to which it is automatically reset after each trainmovement, and coding in a direction oppositetothisprevailing direction isy established: when desired. in response to a manual control to clear an enteringsignal by stopping such coding in the prevailing direction at the transmitting-v end, provided the coding in the prevailing' direction is not being used to clear the.v other enteringI signal and inverse or off code pulses arebeing. received atv said transmitting'end.'

Another featureof the invention relatestoindicating automatically in the remote-control'l of.4 lice; ofthe C. T.` C'. systemthe-.occupied or unoccupied condition of the siding sections and the single track stretches between` the. ends of the passing sidings. In the? case ofthe sidingsections, aseries or-approach relay\responsiveito a wheel shunt isemployed' for governing? theoperation of; the C. T. C. system to transmit an occupancyindication to the control-'oiiice In the case ofthe single trackstretches, an indication control relay ateach en dofl the stretchis arranged to be energized whenever the stretch becomes occupied by a train tocause transmissionk ofan occupancy-indication to the-control office, and this relay isP maintainedY energized untilthe stretch becomes unoccupied.

Inanother embodiment of the invention constitutinga Ymodification orvariation, instead'of leaving thel system normallyv coding after each train movementV to transmit code pulses suitable forY clearing signals for one direction of tra-n movement, provision is made to automatically stop or shut down the track circuitcodingY after each train movement, whenlsuchcodinglis' no longer needed for signal clearingpur'pos'es, this Vshut-down function being performed'by transmitting a single shut-down pulse-ofV limited duration, in opposition-to thedirection offcoding-left behind xa train, and thereby release ,the code sendingrelaythen energized'tc cause theA system to assume, a normally deenergized and inactive condition, When itis required to; clear some 'signal for a desired train,movernent-afterV the system liasv.vthi1s been shut down, provision is made for automatically initiating track circuitcoding-in the y,proper direction-in response'tott-he supervisory maniialgcontroiofgthe,C: T." C; system to clear such;signal.'-` Inthe case of Vthe'v single track' stretches between,l theends of-passing sidingS, C Q'Slllg .Operation is initiated after, the system" has been shut down 'at either selectedj endVv ofthe stretch when a signal' clearing controlv is exercised by the C; T. C; system for the oppositeend of the stretch; but in the case of, the siding setions opposite the passing sidings, track circuit coding in the required direction is automatically initiated after the system has been shut down by transmitting a start pulse over the track rails from; the end gof.A the siding` section at which a signal clearingcontrol is-exercised bythe C. T. C. system.

Since the track circuits and-associated coding equipment. areV not energized or operating in this other embodiment of the invention, except while signals are being cleared for some desired train movemennit islappa'rent that a substantial saving in current-'consumption and in the Wear on the contacts and other moving parts of the coding. equipment isgobtained. This normally inactiveorfshut-down equipment of the invention pro- Videsf r:;back,uptrain moves under supervisory manual, control, for train movements into and out of-outlying track switches, and for the transn mission of indications ofoccupancy of the differentl portions of'tracki to the control office, and otherwise affords the samefacility and safety of trainy movement as in the normally coding form of the invention.

Various other characteristic, features, attributes and advantages of the invention will be` pointed out in detail hereinafter and: willalso be apparent as the description progresses.

The accompanying drawings illustrate certain specific embodiments of: the invention in a sim.- plied and diagrammatic manner, and.V are arrangedY to. facilitate an explanation and: understanding of the nature and mode ofoperation of the system rather than showin detail-the con-- struction and arrangements 1. preferably employed in practice.

In describing the invention, referencewillbe made to the accompanying.. drawings in which those parts-having similar features andfunctions are designated throughouty the several illustrations` by like letter reference characters which are generally made distinctive. by reason o preceding numerals indicative offthe locationcffthe signal with which such parts-,are associated, and in which:

Figs. 1A, 1B, 1C" andV 1D, when', arranged; end toend, illustrate the system offthis-invention as applied to a typical stretch of single track between the ends of passing sidings, andalso one siding section;

Figs. 2A to 2F-comprise a series of explanatory diagrams illustratingvarious operating characteristics ofthe embodimentofthe invention shown in Figs. 1A to 1D;

Fig; 3i1lustrates conventionally andI diagrammaticallythe control panel andcertain features of control equipment for a, particular type of coded C. T. C. system suitable for'governing the signals andthe direction of.v track circuit coding for the embodiment of the invention shown in Fig. l;

Figmly shows diagrammatically a typical arrangement for thecontrol of avpower operated track switch together-'with the. time release stick locking associated withY such switch; and

Figs. 5A, 5B; 5Ctand;5D; when placed end` to end, illustrate a modification/ofthe:system of the present invention and embodying the shut-down feature mentionedf above.`V

In thesedrawings relays and contacts have been shown ina conventionalmanner, and to facilitate the illustration inv somelinstan'ces contacts of relaysareillustrated at a dierent place onthe drawings-than the'winding of the relay. Also, to simplify-theillustration of cir- Cults; Connections with the opposite terminals -of a battery or other suitable source of current for energizing local circuits have been represented by the symbols and associated with arrows.

General organization-For the specifiic embodiments of the invention illustrated, it is assumed that the invention is applied to a typical or conventional single track railroad comprising single track stretches between the ends of passing sidings and siding sections constituting the portions of the main track opposite the passing sidings. It is also assumed that the switches at the ends of the passing sidings Will be power operated in the usual manner by switch machines under the supervisory manual control of the; C. T. C. system, although it should be understood that the system may be used in connection with hand operated switches.

Figs. 1A to 1D inclusive, when arranged end to end, show the apparatus and circuits for a, single track stretch between the siding ends A and B, with starting or head-block signals I and IA, governing east-bound train movement into the stretch; starting signals 8 and 8A governing west-bound train movement into the stretch; entering signals 2 and 2A govern west-bound train movements while entering signals 1 and 'IA govern east-bound train movement out of the stretch over their respective switches in normal or reverse positions; and two pairs of opposite intermediate signals 3, 4, and 5, 5. At each siding end is a detector track circuit AT and BT, which is of the usual normally and steadily energized type. It should be understood that the arrangement and location oi signals illustrated is merely.`

typical and that the inventi-on may be applied I to other arrangements.

In the conventional arrangement of tracks iol' single track railroads as assumed, a siding section or portion of main track is associated withv each passing siding; and while the two ends of such siding sections shown in Figs. 1A and 1D are physically diierent portions of track, it is convenient to assume, in order to avoid unnecessary duplication of drawings, that the relays and.

circuits shown in these Figs. 1A and 1B belong to the opposite ends of the same siding section designated 1-2T, so that the circuit organization for one complete siding section is shown when Figs. 1D and 1A are arranged end to end.

These signals may be of any suitable type, but for simplicity in the illustration of their control circuits are assumed to be color light signals Which display green, yellow, and red lights for proceed, caution, and stop indications when the lamps G, Y, and R are lighted by the circuits shown. Color light signals of the so-called search light type, such as disclosed, for example, in the patent to Field, No. 2,097,785, dated November 2, 1937, may be controlled from the same home and distant relays H and D shown in the manner disclosed in my prior application, Ser.

No. 439,520, filed April 13, 1941.

The starting of head-block signals I, IA and 8, 8A and also the entering signals 2, 2A, and' 1, 7A, if power operated switches are used, are arranged to display in accordance with established practice absolute stop-and-stay indications, while the intermediate signals 3, 4, 5, and 6 are arranged to display permissive stop indications, such as by the vertical or staggered relation of the signal light with a marker light.

yIn the embodiment of the invention shown, ar-

rangement is made for approach lighting and intermediate signals in a manner later explained;l

'and if desired the same expedient may be employed for approach lighting the entering signals such as 2, 2A and the high speed starting signals such as I. The side track or portions thereof may also be equipped, if desired, with track circuits -to provide approach lighting for the low speed signals IA and 8A governing train movement oi of the siding.

The C. T. C. system required for the control of the signals and direction of track circuit coding may be of any suitable form capable of governing the energization of signal clearing relays at the siding ends, and also controlling the power operati-on of the associated switch machines ASM and BSM, if used. It has been assumed that the C. T. C. system will be of the code type acting to transmit during a control cycle a series ofl distinctive code elements for station selection and switch and signal control. This system also operates during an indication cycle to send to the control oice a series of distinctive code elements identifying the particular eld station sending, and also constituting indications of switch position, signal clearing, and track occupancy. As a tangible example of a code C. T. C. system of this character, it has been assumed that the apparatus and circuits as illustrated will be controlled by a two-wire code C. T. C. system such as disclosed in the patent to Hailes et al.,

Patent No. 2,259,561, granted October 21, 1941, and also illustrated and described in Centralized Traflic Control Handbook 20 of the General Rail- 'way Signal Company, copyrighted 1941.

It is contemplated that the control ofiice equipment of the C. T. C. system will include the usual control machine having on its control panel a miniature track diagram of the railroad, as diagrammatically illustrated in Fig. 3 with the usual two-position switch levers such as AWL and BWL for the switches at each end of the passing sidings; three-position signal levers such as AGL and BGL governing the signals associated with each siding end, together with suitable start buttons ASB and BSB associated with each lever group or panel. Indications of the switch operation may be displayed by a correspondence lamp in the switch lever as disclosed in my prior Patent No. 2,038,128, dated April 21, 1936, or in any other suitable manner. Indications of the clear or stop condition of the signals may be displayed by. lamps located in the signal levers or otherwise associated therewith or by lighting lamps in miniature representations of the signals on the track diagram as disclosed for example in the patent to Phinney, No. 2,215,407, dated September 17, 1940. In addition to the usual track occupancy lamps associated with the detector track sections, it is proposed in accordance with this invention to provide a lamp for each siding section and each single track stretch to indicate occupancy of these respective portions of the track when lighted. Fig. 3 also illustrates diagrammatically a special arrangement of change and code determining relays governed by the start buttons which provides the desired transmission v of control codes to different field stations for the purposes of this invention, as explained hereinafter.

Each of the siding sections and each block between the signals is provided with a coded track 'circuit equipment similar to and involving the same operating principles as the conventional and well-known coded track circuit. Each of vthese coded track circuits comprises a source of current A(assumed to be a battery), a code following track relay TR,-and a transmitter relay -CTP for each end of the trac'k section. The-.code transmitter relay CTP is arranged `to be operatively connected to codingcontacts-C `of afsuitable code oscillator or equivalent which are intermittently operated in the usual way at a `pre-- determined code rate; and when the transmitter relay is thus energized and deenergize'd it con- Ynects the source of current and the track relay respectively across the track rails alternately at a rate determined by the oscillator cont-actswith which the transmitter relay is then connected.

.Each track relay TR directly, or by the opera- Ytion of a repeater relay, governs the energization of a decoding transformer in the usual'way to cause energization of a signal control home relay H in response to the coding operation of the track relay at any rate for giving `a caution indication, and causingenergization of asigna] Vcontrol distant relay D in response to coding operation of the track relay at a predetermined proceed or clear code rate, all in the manner that will be readily apparent to those skilled in the art. It is assumed that code pulses at therate of 75 per minute will be employed for caution.

signal control, and at the rate of '120 for clear signal control, an extra clear code rate of 180 being also preferable employed in connection with the end track sections of the stretch for purposes later explained. These 75, 120 and 180 code rates j :are determined by oscillator or codingcontacts 15C, IZBC and lC'respecti'vely.

In one arrangement of control circuits for the intermediate signals, as shown in Figs. 1B and 1C, there is only one H relayA and one D relay for -each pair of intermediate signals; and these lrelays H 'and D govern the indications of one orthe yother of these signals selected-in accordance with the energization of coding direction relays WC and EC, which also perform the functions ordirectional stick relays for these signals.

The power operation of the switch rand the clearing of the signals at each siding end infresponse to supervisory manual control may be governed in any suitable manner by the C. T. C. system; and one typical arrangement suitable for this purpose, based upon the disclosure of the patent to Wells, Patent No. 2,159,922, May 23,

v1939, is illustrated in Fig 4 for the siding end A. Referring to this Fig. 4, the signal clearing relays ARD and ALD for governing the'clearing of signals I, IA and 2, 2A for train movement to .the right and left respectively, and the switch control relays AWN or AWR controlling the power operation of the switch to the normal and reverse position respectively, are governed bythe code C. T. C. system in the manner fully explained in the Wells patent above mentioned, and for the purpose of understanding the presentinvention a brief. summary of this operation willbe suilicient.

When the signal lever AGL in Fig. 3 .is operated to the right or to the left and a control code is transmitted, the lower winding of the corresponding signal clearing relay ARD or ALD is ener- .gized for train movement in a corresponding direction to the right or to the left; and `When-a control code is transmitted with the signal lever ALG in the midde or stop position, the relay ARD or ALD then energized is manually restored vto the deenergized position by the neutralization or `differential action effected by energizing its upper winding.

Each signal clearing relay ARD and ALD-.hasi'a s ticklcircuit through its lower winding governed.

rtrol.

by affront contact .86' of the detector track relay vATRandfa back contact'vtl I of'itsslow repeater relay-ATRP, so that therelay ARD or ALD then energized is automatically restored to itsdeenerrgized condition by the entrance of a-.train intov the detector track section to'drop the' detector track relay ATR, and also so'that either of these relays, if energized-by C. T. C. control while the .detector track section is occupied, will be held up after the'trainleaves, `all'in'a manner more fully .explained'in .the Wells `patent abovementioned.

The switch control' relays AWN and yAWR are selectively energized by the C. T. C. code system in accordance -with the operated position of the .switch lever AWLof Fig. 3, each of these relays vbeing maintained energized by a stick circuit until the other is energized by manual con- "Also, the circuits Vfor energizing the upper lwindings of the relay-AWN or AWR by C. T C.

control include back contacts v53 and 55 of the signal clearing relays ARD and ALD, so thatno C `T.-C;' contro'lto changethe position of the switch is effective while Va signal clearing control lisr exercised. These switch control relays AWN and AWRcontrol by their contacts 6I and'IiZthe application of operating current-to an electrically operated switch machine ASM ofthe usual type to cause power operation of'the switch to the corresponding normal or reverseposition, provided 4such operation is safe and a lock relay ALRis 'energized to close its front contact El).

When the position ofthe switch, as manifested by the condition of a relay. AWP governed in the usual way in accordance with vthe position and locked condition of the switch, matches the existing control exercised by the .switch control-relay AWN or AWR then energized, a corresponding normal or reverse correspondence relay ANCR or ARCR is energized by circuits easily traced on ythe drawing; and these correspondence relays ANCR and ARCA govern the clearing of the associated 'signals in the usual manner as Villustrated in Fig. 1A.

While special provisions may be made for approach locking control of the switch, such as 'by providing inverse codes inzthe manner disclosed for example in my prior application, Ser. No. 439,520, filed April 18, 1942,above mentioned, 'in the interests of simplicity, it has been assumed in the disclosure vof the present invention that time release -stick lockingwill ybe employed, and one typical arrangement for this purpose is diagrammatically shown in Fig. 4. Referring to Fig.

4, the power circuits for the switch machine ASM, governed by the `switch control relays AWN and AWR, are opened'at the front contact 60 of a lock relay ALR when this. relay is deenergized by opening its normally closed circuit upon opening contacts B3 and 64 by the. release of either of the lock stick relays ILS or 2LS for the signals I, IA, and 2, 2A governing train movement over the switch, or upon opening of contact 65 by the release of the detector track relay ATR. This en- -ergizing circuit'for the lock relay ALR may be readily traced oni the drawings.

The lock stick'relays ILS and 2LS and their r`:associated time element devices ITE andfZTE, together with back contacts of -the-detectortrack relay, provide stick locking with time release :and detector track circuit release in the well known'manner.. For example, when either signal relay IG;or IAGI-ls energized to clear the assorciated-signalgfthestick circuitv for the relay ILS readily traced on the drawings through contacts 56, S1 and 68 is broken; and when the signal is manually put to stop, current is supplied through the back contact 68 of this relay ILS to its time element device ITE to close its contacts S9 after a prescribed time interval to allow re-energization of the relay ILS. When the signal is put to stop by a train entering the detector track section, the back contact of the detector track relay ATR allows the lock stick relay ILS to be re-energized immediately. A

Although the circuits and apparatus of Fig. 4 have been described as associated with the siding end A, it is to be clearly understood that similar circuits and apparatus are assumed to be associated with siding end B, and all others of a complete system. Also, all operations mentioned in connection with this Fig. 4 are to be considered typical of all other siding ends.

Normal conditions- In the embodiment of the invention illustrated in Figs. 1A to 1D, driven code pulses are transmitted under normal conditions over the track rails of the track sections of the single track stretch in a direction dependent upon the direction of the last train movement through the stretch, as shown in the diagrams of Figs. 2A and 2B; but for the showing in Figs. 1A to 1D it has been assumed that the last train movement through the stretch was east-bound leaving the track sections coding in a west-bound direction as indicated by the solid arrows in said Figs. 1A to 1D as well as in the diagram of Fig. 2A. Under normal conditions, driven code pulses are transmitted over the track rails of the siding section in a predetermined prevailing direction assumed to be West-bound as shown in the diagram of Figs. 2A and 2B and indicated by the solid arrows in Figs. 1A and 1D; and there are also inverse .or off-code pulses in the track rails of this siding section in the opposite direction as indicated by the dotted arrows in those figures.

In many respects the arrangement of relays and operating circuits are the same for the siding ends and intermediate signal locations; and it is convenient and helpful to assign the same reference numbers to corresponding contacts for the different relays without differentiating between the locations where these contacts are used. Also, in connection with the use of reference numbers on the drawings, for the purpose of convenient ref? erence, a number of the wires and contacts in Fig. 3 corresponding with those disclosed in the Hailes et al. Patent No. 2,259,561, October 21, 1941, are given the same reference numbers used in this Patent; and the same is true for various parts shown in Fig. 4 corresponding with those disclosed in the Wells Patent No. 2,159,922, May 23, 1939.

The direction of coding in the single track stretch under the normal conditions assumed, is due to the fact that the code sending stick relay BCS in Fig. 1D, which was energized by manual control exercised by the C. T. C. system (in a manner later discussed) at the time the signals were cleared for the prior eastbound train movement assumed. it being maintained energized by a stick circuit closed through the back contact I2 of the code following track relay BTR, and front contact I3 of relay BCS. With the code sending relay BCS thus maintained energized, the transmitter relay BCTP is intermittently energized at the 75 code rate by a circuit which may be traced from (-i-l through front contact I4 of the lock stick relay SLS associated with signals 8 and 8A,

, SEC, to

coding contacts of an oscillator 15C operating at the 75 code rate, back contact I5 of signal relay 1G, front contact IS of relay SCS through winding of transmitter relay SCTP, to

This application of driven code pulses at the east end of the end track section 5-8T causes coding operation of the code following track relay STR at the other end (see Fig. 1C) which intermittently energizes through its front contact l a front contact repeater relay ETP. The track repeater relay STP is made sufciently slow releasing, while relatively quick to pick up in any suitable manner as by being shunted by a rectiner, so as to hold its front contacts closed during the coding operation of the track relay STR.

With the track relay repeater 5TP energized, the coding direction relay SWC is energized by a pickeup circuit which may be traced from thrcugh front contact 20 of relay STP, relay SWC, back contact 2l of other coding direction relay Under these conditions, a quick acting track repeater relay 5-STP is energized each time the track relay ETR drops over a circuit closed from through back contact I8 of track relay STR, front contact 22 of relay BTP, back contact 23 of relay SEC, and front contact 2d of relay SWC, windings of relay 5--STP, to The intermittent operation of the contact finger 25 of the repeater relay 5-STP energizes alternately the two halves of the primary of the decoding transformer 26, and causes intermittent energization of the home relay 5--SH by impulses in the secondary of this transformer rectied by front and back contacts of contact nger 2'I of the repeater relay S-STP in a manner familiar to those skilled in'the art. The home relay -SH has the usual slow release characteristics so as to maintain its armature steadily in the attracted'position during the coding operation of the repeater relay E-STP.

With the relays SWC and 5--SH energized, the transmitter relay SCTP for the track section 3-6T is connected to coding contacts operating at the I2Il rate through a circuit which may be traced from through back contact I8 of track relay STR, back contact 22 of its slow release front contact repeater STP, coding contacts IZUC, front contact 32 of relay .5-SH, and front contact 33 of relay SWC, winding of code transmitting relay SCTP, to

These driven code pulsesapplied to the east or righthand end of the track section 3-ST cause coding operation of the code following track relay 3TR in Fig. 1B; and at the signal location 3 circuits similar to those described for signal location 5 result in the energization of the track relay repeater BTP, intermittent operation of the track repeater relay 3--4TP, and energization of relays 4WC and 34H. Also, since the proceed 120 code rate is being supplied to this track section 3-BT, the relay 3-4D at signal 3 is also energized through the agency of its tuned decoding circuit and rectifier in the usual manner.

Under these conditions, with relays IIWC, 3-4H and 3-4D at the signal location 3 energized, the transmitter relay 4CTP for track section I-4T is operated at the code rate by a circuit similar to that described for signal location 5 and readily traced on the drawings through back contacts I8 and 22 of relays IITR and 4TP, coding contacts ISSC, front contact 48 of distant relay 3-4D, front contacts 32 and 33 of relays 3--4H and IIWC, relay IICTP, to This causes coding operation of the track relay ITlFil in Fig. 1A

gaat

11 and its quickactin-g repeater ITP at the siding end-A, thereby. energizing relay IH, and also relay IDX responsiveto the 180 code rate.

Considering now the normal condition of coding inthe siding section, and referring to Figs. 113` and 7A arranged endzto end to show the complete siding, transmittervrelay 2CTP at the east or right-hand end of the siding section 1 -2T isconnected. to the coding, contacts operating at the 75-code rate by a circuit which may be traced from ('l-) through a front contact 34 of the lock stickrelayZLS for signals 2 and 2A, coding contacts.l5`C, back contact 35 of signal relay IG, front contactiotdetector track relay ATR, back contactl 3.1 of' the correspondence relay ARCR, back conta'ctiBof' a code reversing relay CR, relay ZCTP, tol-.

This'transmission of driven code pulses west for` the prevailing direction assumed over the track rails` oi the siding track section '1 -2T causes coding operation of the track relay lTR and energization ofi its slow release front contact repeater; relay TTF, which in this instance is connectedin series with the upper half of the decoding transformer.` Likewise, signal control relay. IH is energized, but not the relay 1D, since the 'I5` caution coderatewis being transmitted.

Provisionis also made for transmitting over the track'. rails of the siding section inverse or ofi code pulses for the purpose ofv providing an interlock between-the' opposing entering signals 1f and 2 as later. explained; In the arrangement shown, these'inverse. codepulses are created by animpulse secondary. winding 1I on the decoding transformer 12 which actseach time on the track relay 'ITR- drops -to'prov-ide a current impulse for momentarily; energizing the transmitter relay 'ICTP-over a circuit which may be traced from said impulse winding 1-I` through back contact 13 of the signal clearing relay BRD, front contact 'I4 o f-the lock stick relay ILS, front contact 150i repeater relay 1TP, transmitter relay ICT-P, to the. sameV terminal. The transmitter relay 'ICTP is of fa biased polarized type so that it isenergized to operate its contacts only by an impulse of the particular polarity which exists when the track relay "ITR releases.

These. inverse or off," code pulses, which are transmitted in the usualway during the oft intervals of the driven codeY in the siding track section, cause. intermittent operation of the code following track relay ZTR (Fig. 1A) at the opposite end of the siding section from which the driven code pulses are being transmitted, and through vthe usual decodingtransformer connection causes energization ofthe signal control relay 2H.

Under the normalconditions under discussi-on, the transmission of west-bound driven code pulses inthe track sections of the single track stretch and the 'energization' of the west code direction rela-ysAWC and SWC (Figs. 1B and 1C) prepare circuits for causing the intermediate signals 3 and Sito display green or clear and yellow or caution indicationsrespectively as shown in the diagram` of Fig. 2A; but these signals are preferably arranged as shown to be approach lighted, so that no -indications lfor these intermediate signals are actually shown. The signals at the sidingends are also at,v stop under normal conditions, since'the-signal clearing relays ARD and BRD manually controlled by the C. T. C. systemv are deenergized, although driven codes are being transmitted in a direction to clear such signals for east-bound train movements.

c'. YT. C. control.ofeignazezearmg and'direction;

of track circuitcoding-1n accordance witlitliis invention, whena supervisory manual'control' is.-

exercisedover the C.- T. C. system to clear a head.- block signal at a selected end ofthe single trackA stretch between passingsidings, a control is likewise exercised tol initiate operation of a code,

sending means at the opposite end of this single' track stretch. This plan of operation is characteristic of the system disclosed in my prior application, Ser. No. 439,520, led April 18, 1942; and if desired the same organization disclosed in that application may be employed in'connectionv with the present invention toV control the ener-'- gization of the signal olearin'g'relay `ARD or BLD at a selected end of the single track stretch andr energization of a signal clearing relay ARD or BLD (Figs. 1AV and 10) at the C. T. C eld station at'one siding end during one operating cycle, and energization of the code sending relay CS at the C. T. C. field station at the other siding end during another operating cycle. In other words, in the arrangement disclosed, provision is madeto cause the code C. T. C. system to'operate through two operating cycles when the operator desires' to senda train into thesingle track stretch, and to transmit to one field station on one operating cycle a signal clearing control, 'and to a'diiferent field station during the other operating'cyclefa code starting control.'

Considering this proposed' organization of a code C.' T. C. system, it isA an operating charac., teristic of this type of system that during'each operating cycle for transmission of controlsone particularV eld station is; selected in accordance with the character of the. code elements transmitted during a numberofstation selecting steps, corresponding'with a particular group of levers manually actuated by the operator and requiring the transmission of new switch and/or signal controls,

Intheparticular type ofcode C. T. C. system disclosed in'. the patent to Halles et al, No. 2,259,561, October 21, 1941, and selected as the basis: for the present disclosure, the system is normallyatrest and is set into operation by actuation' of` start buttons which control the energizationof a group of change and code determining relays so asto transmit control cycles irna; predetermined.'v sequence for the levers having start buttons actuated. Also, in this particular system, the character of the control elementsfor: transmission oil distinctive controls is determinedbyfthe polarity of energization of the linecircuit: andsignal control codes for theen.- ergization andrelease'of relays RDand LD for each fieldV station are transmitted on two control steps,sayf(l) forRD energization, for iiD-energization, and (-l-l) for stop signal control, as explainedy fully in the patent to Wells,l No. 2,159,922, May'23, 1939. This leaves the code combination of on these-signal control steps available for performing other functions; and in accordance with this invention it is propcsedrtouse this extra control code for the-energization of thecode sending stick relay CS associated witlithel corresponding held station.

The additions and variations of the code C. T. C. system disclosed in the patent to Hailes et al., No. 2,259,561, for accomplishing this purpose relate to the starting and code determining circuits to provide for starting and transmission of this extra control code to the eld station at one siding end when the start button for the eld station at the other siding end is actuated at a time While its signal lever is positioned for train movement into the single track stretch. For this purpose, the starting and code determining relays and circuits in the control olce shown in Fig, 2 of the Hailes Patent No. 2,259,561 are modiiied as illustrated in the accompanying Fig. 3, more particularly by the addition of auxiliary change relays such as ACHX for each eld station group of levers.

Considering the operation of this control oiice equipment of Fig. 3 in the case of a West-bound train movement, when the operator actuates start button BSB, after positioning the signal lever BGL to the left, the change relay BCH for the siding end B is energized in the usual way and also the auxiliary change relay ACHX for the field station at the other siding end A is energized by a circuit from (-l) through contact 5I of signal lever BGL to the left, contact 52 of start button BSB and lower Winding of relay ACHX, to and closing of the front contact 54 of relay ACHX also causes energization of the regular change relay ACH through the normally closed contact 51 of the start button ASB, winding of relay ACH, normally closed contact of the cancel button CN, to

In this way, upon actuation of the start button BSB, when the signal lever BGL is set to the left, the change relay ACH for the field station associated with the other end of the single track stretch and its auxiliary change relay ACHX is also energized at the saine time the regular change relay BCI-I is picked up. 'If the code C. T. C. system is at rest, or as soon as an existing operating cycle is completed, the code determining relay such as ACD is energized if its associated change relay such as ACH is energized, dependent upon the arrangement of these relays in the interlocking circuits. As illustrated, in accordance with the disclosure of the Hailes et al. patent, code determining relay BCD has a priority in the sequence of control code transmission over code determining relay ACD; but the operation under consideration would be substantially the same if the priority were different by a different arrangement of the interlocking circuits.

, Referring to Fig. 3, and assuming the code C. T. C. system is at rest as shown, the energization of the change relay BCH by actuation of the start button BSB as just described, closes a circuit to energize the code determining relay BCD which may be traced from (-l) through back Contact 4| of relay SC, back contact 42 of relay C, back contact 43 of relay CDS, front contact 44 of relay BCH, upper winding of relay BCD, through the cancel button CN to The energization of the relay BCD opens at its back contact 58 the stick circuit for the change relay BCH, and at the same time closes a front contact 59 to provide a stick circuit through the lower Winding of relay BCD in series with the relay CDS. Thus, while the change relay BCH is deenergized, the relay CDS is energized to open its back contact 43 and prevent energization of any other code determining relay. This operation is described more in detail in the Hailes et al. patent above mentioned.

When the code determining relay yBCD belonging to the iield station of the C. T, C. code system at the siding end B of Fig. 1D is thus energized, the system operates in the manner explained in detail in the Hailes et al. patent to select this particular eld station, and on certain control steps transmit (-l-l or code elements to provide the desired controls for clearing signals or initiating operation of track circuit coding. In the simplified arrangement illustrated, it is assumed that steps I, 2 and 3 of the operating cycle are allocated to station selection and step 4 to switch machine control, in conformity With the disclosure of the Hailes et al. patent above mentioned, and that steps 5 and 6 corresponding with the energization of step relays V5 and V6 are utilized for signal control.

Under the conditions assumed, With the code determining relay BCD energized and the signal lever BGL set to the left-hand position, a control code of Will be transmitted on steps 5 and 5 to the field station at siding end B (Fig. 1D) to cause energization of the signal clearing relay BLD. Considering how this particular polarity of these code elements is determined, when the step relay V5 is energized, the relay NC giving a code element is energized by a circuit which may be traced from through back contact of relay LV, back contact S2 of step relay V5, front contact 83 of step relay V5, code bus 85, front contact |98 of relay BCD, back contact |99 of relay BCHX, contacts of signal lever BGL to the left, to bus 9B and relay NC to A similar circuit for energizing the relay PC giving a (-l-) code element is established on the sixth step when step relay V6 is energized.

Thus, under the particular conditions assumed, and with the arrangement of interlocking circuits for the code determining relays illustrated, the rst operating cycle of the system causes transmission ol a signal clearing control code ci -l) to the field station at siding end B.

When the relay LV in Fig. 3 is energized at the end of this operating cycle, the opening of its back contact 46, with the relays C and SC energized at this time to open their back contacts 48 and 49, interrupts the stick circuit for relay BCD in series with the relay CDS, thereby releasing relay BCDy and closing at the back contact 43 of relay CDS the circuit for energizing code determining relay ACD through front contact 45 of relay ACH, when the operating cycle is cornpleted and relay C and SC have released to close their back contacts 42 and 4l.

The energization of the code determining relay ACD opens at its back Contact |51 the stick circuit for the change relay ACH and at the same time establishes through its front contact lill a supplemental stick circuit for the auxiliary change relay ACHX. The code C. T. C. system now operates in the regular manner as described in the Hailes et al. patent to select the field station at the other siding end A, and transmit on steps 5 and E a control code of for energization of the code sending relay iCS at this siding end A (see Fig. 1A) The circuit for energizing the relay NC on step 5 corresponding with a code element may be traced from through back contact 8U of relay LV, back Contact 82 `of step relay V6, front contact 83 of step relay V5, code bus 85, front contact 8l of relay ACD, front contact 88 of relay ACHX to bus 9D, and relay NC to A circuit for energizing the relay NC to give a code element on the other step 6 when relay V5 is energized is similar to that just traced.

An. operation of the C; T. C..systeni similar to that just described occurs when the signal lever AGL isset tothe right and'thestartbutton ASB interlocking circuits asV illustrated, the signal clearing-,controllis transmitted on the second op eratingf cycle' of the C'. T. C. system, and the control tov initiate the track circuitl coding on a prior operating" cycle; but it can be appreciated thatthe order inf which-the signal clearing andy codefstarting controls are transmitted is not material in the operation of the system, since the head-block signal being controlled-cannot clear until a clearing trackcircuitcode issreceiv'ed :ands also its signalclearing relay ARD or BLD vis ener-v gized.

Operation for ani east-bound train movement-Havingv outlinedthe mode of operation With-respect to the C. T. C. control for signal clearing and initiation of track circuit coding" for the single track stretch between sidings, consideration may now be given to the operation of the system'for typical train movements; and to illustrate certain operating'characteristicsof the invention it is expedient to assume that, underl the normal operating condtions'shown in theVv drawings, and with the track'circuit ycodingvexist'- ing. in a direction for east-bound train move-` ments, the operator desires to -sen'd another: eastbound train from' thevsiding end Af of Fig.- lA toY siding end B, acon'trol code-fori energizing thej code sending stick relay BCS. Under'the condi-Y tions assumed, however, the rela'yj'SCS is-already energized, so that such-controlcode can perform no useful work, and relay SCS remains'energized over its stick circuit- Thus, driven code pulses are -transmittedrv over the track sections ofthe single' track' st'retchto'- ward siding end A, This results in the energizationof the relays IHand'lDXat sidin'g'end'A (see Fig. 1A), so that either' the headeb'lock'signal I or IA maybe clearedby manual control over the C. T. C. system.

Referring to'Fig.' 1A and considering the operation occurringat siding end A' as a result of the energizationfofthe signal clearingLrelay ARD, the closing of frontc'ontact 94' ofthis'relay ARD closes theY circuit to energize rela'y IG or relay IAG to clear signal-lor' IA as the case 'may be;

vdependent upon the'. position of the switch. In

the case assumed, the switch is supposedtobe operated to tnev reverse positionand' when this occurs relay IAG is-energized .by'a circuit which may be traced from through back contact 9| of code sending relay ICS,V front contact 92 of signal control relayV IH, frontv contact 93 of detector trackrelay ATR., front contact 94 of'ree lay ARD, back contact g-otnormallco'rrespondencerelay ANCR, front contact 96-A of reverse 16' correspondence relay ARCR, relay IIAG, to Signalv IA having thus been cleared, the train in question assumedto be on the siding may now advance into the detector track section AT.

This releases the relay ARD by opening front contact 86 ofy the detector track relay ATR before the hack contact ||I of its slow release repeater relay ATRP closes, to provide stick signalcontrol, The opening of frontcontact 93 of thedetectortrack relay ATR. also acts to deenergize relay- IAG and put the signal IA to stop.

This does not interferey with the coding in thesiding section', because under these conditions the reverse correspondence relay ARCR is energized, closing itsA front contact 3l to connect the oscillator coding contacts to the transmitter relay 2CTP independently of the position of the contact 3S of the detector track relay ATR.

When the east-bound train in question enters the first track section |-4T of the stretch of singleA track, it shunts the track relay ITR and stops'its coding operation, thereby dropping re lay- IH- to open at itsfront contact 92 the ener'- gizin'g'" circuit for signal relay IAG and maintain signalv IA- at stop while this track section isV occupied.

When the east-bound train in `question entersthe iirst track section |-4T, or at least after it has advanced part way into this track section; depending upon operating conditions, the shunting effect of its wheels and axles increases`-the flow of current through the series relayv SSRk at the east end of thisY track section (see Fig. 1B) and causes this relay to' close its front contact` 91 and approach light the signal 3i Under the conditions assumed, the coding. direction relay AWC is energized, and the home relay' 3;-4H andthe distant relay 3--4D are en. ergize'dbythe clear code being transmitted west inl track section 3-5T toward the signal 3, so that' the greenlamp of signal 3 is lighted over a circuit readily traced through the front contac'ts' Si, 98', 99 and |08 of the relays IISR, 4WC, 3441i-, 3---4D.

Inthe arrangement shown, the series relay QSRiuiion'closing its front contact |02 establishes astiok circuit for holdingit energized as long asf'thewheel shunt exists independently of the coding operation of the transmitter'relay 4CTP, thiseXpedient being employed so that this series relay GSR does not needV t'o have slow release characteristics'to holdup during codingopera'tiOn. or have'a slow release repeater relay. In order that this series relay at'SR; may not erroneously energize itsA associated track relay, it opens at its back contact |63 the circuit thr'oughth'e code following track' relay 4TH, this also incidentally constituting aclieck to assure that the series relay' releases'a-fter each train movement, otherwise no code'can bereceived at the corresponding sig.- nal loc-ation;

Theenergization of the series-- relay 4SR also forms anv auxiliary stickv circuit for the coding' direction relay AWC from C+), through front contact `il'of relay 4SR, back Contact |05 of repeater relay 4TP, front contact |06 of relay 4WC, windingof this relayl IIWC, and back contaet- 2| ofy relay SEC, to Consequently, when atrain passes the signal 3 and shunts track relay 3TR and releases its repeater relay 3TP, the coding direction relay 4WC is maintained energized by this auxiliary stick circuit until thesignal relay 3-'4H releases and closes atV its back contact |01 a permanent stick circuit readily traced for relay 4WC. In this cori-v nection, it should be understood that the track relay repeater 3TP is arranged to have a substantially shorter release time than the signal relay 3-4I-I, say .6 of a second as compared with 15 seconds, so that when the coding operation of the track relay 3TR ceases under other circumstances when the series relay 4SR is not energized by an approaching train, the coding direction relay 4WC drops, because its pick-up circuit is broken at the front contact 20 of relay 3TP before its stick circuit is established at the back contact I01 of relay 3-4H.

By reason of this special control of the coding direction relay 4WC, it performs the functions of a directional stick relay as commonly employed in single track signaling systems; east-bound train in question has passed entirely into the track section 3-5T in advance of the signal 3, a code at the 75 rate is delivered to the track section I 4T in the rear of this signal with the relay 4WC energized to close its front contact 33, and the relay 3-4H deenergized closing its back contact 32, thereby providing a caution code in the rear of the east-bound signal 3 to permit the head-block signal I or IA to be cleared for a following train movement if desired, as shown in the diagram of Fig. 2C.

When the east-bound train in question enters track section 3-6T, the series relay BSR for the east end of this track section is energized to approach light the signal 5 (Fig. 1C) and provide an auxiliary stick circuit for the relay SWC in the same manner just explained. Under the normal conditions as shown in the diagram of Fig, 2C, the signal 5 will display a caution indication, since the entering signals 1 and 1A are at stop; but under ordinary circumstances the operator will have previously positioned the switch and signal levers for the siding end B to clear one of the entering signals 1 or 1A for the train in question to enter the siding section or passing siding, as the case may be.

Assume, for example, that the operator causes energization of the signal clearing relay BRD (see Fig. 1D) for movement of the east-bound train in question into the siding section. The closing of the front contact of this relay BRD closes a circuit for energizing signal relay 1G to clear signal 1, which may be traced from through front contact I I2 of relay BRD, front Contact II3 of detector relay BTR, front contact II4 of normal correspondence relay BNCR, relay 1G, front contact I I5 of signal control relay 1H, and front contact IIB of relay 1TP, to Since the normal prevailing direction of coding in the siding section is west-bound and signal control relay 1H is energized, the entering signal 1 may be cleared without modifying the direction of coding in the siding section. In a similar way the low speed or diverging signal 1A may be cleared by energization of signal relay 1AG upon energization of the signal clearing relay BRD and closing of its front contact II2 if the switch is operated to the reverse position to close front contact IIB of the reverse correspondence relay BRCR.

When the east-bound train under consideration approaches signal 5, this signal should indicate caution if both of the entering signals 1 and 1A are at stop, or if the entering signal 1A has been cleared by the operator for a train movement into the siding, and should indicate clear onliT if the entering signal 1 has been cleared by the operator for a train movement into the siding section over the switch in the normal posiand aft-er the 18 tion. Thus, as shown in Fig. 1D, the code rates for governing the clear and caution indications of the signal 5 are selected by front and back contacts I 5 of the signal relay 1G.

When the east-bound train in question passes the intermediate signal 5, as shown in the diagram of Fig, 2D, a 75 code rate is transmitted to the intermediate signal 3 in the rear, and the coding operation of the track relay STR (Fig. 1B) picks up its repeater relay STP tc close its front contact 2U and hold up the relay 4WC by its pickup circuit, and also causes energization of the relay 3-4H to increase the code rate in the track section I-dT to the clear rate of 120, thereby permitting the head-block signal I to give a clear indication for a following train movement if desired. It will be noted that the control circuits for the signal I (see Fig. 1A) are organized so that the green lamp G is lighted by the energization of either of the decoding relays ID and IDX responsive respectively to 120 and 180 code rates.

When the east-bound train under consideration passes the entering signal 1 into the detector track section BT at the siding end B (see Fig. 1D) the shunting of the detector track relay BTR releases the signal clearing relay BRD in the usual way, and also opens at its front contact II 3 the energizing circuit for signal relay 1G, so as to hold the signal 1 at stop while the detector track section is occupied, even though the relay BRD might be again energized by a subsequent C. T. C. control code, and although the train being short or a single locomotive, has not advanced into the siding section to drop the signal control relay 1H.

When the east-bound train in question enters the siding track section 1--2T, cessation of the coding operation of the track relay 1TR releases its slow release repeater relay 1TP to connect the code transmitter relay 1CTP through the back contact 15 of relay 1TP, back contact I 20 of relay BG, coding contacts 15C, and front contact I2I of relay BTR, and thus permit relay 1CTP to be intermittently operated when the train leaves the detector track section and front contact I2I of the detector track relay BTR closes, thereby producing driven code pulses under and following the train.

`Considering the operation for the movement of the east-bound train under consideration out of the siding section, and arranging Figs. 1D and 1A end to end to show the circuits for the complete siding, assume that the head-block signal I has been cleared to permit the east-bound train under consideration in the siding track section 1-2T to advance. When this ytrain drops the detector track relay ATR, the transmitter relay/ 2CTP is steadily energized by a circuit from (-l) through the back contact 36 of detector track relay ATR, back contact 31 of correspondence relay ARCR (switch being normal topermit signal I to clear), back contact 38 of relay CR, and relay 2CTP, to When the train clears the siding track section 1-2T, this steady energization of the transmitter relay 2CTP is effective during the rst off period of the driven code being transmitted from the other end to energize the track relay 1TR and its repeater relay 1TP to cut olf at the back contact 15 of relay 1TP such driven code being transmitted in the reverse direction. As soon as the train leaves the detector track section AT, the front contact 36 of the detector track relay ATR connects the transmitter relay 2CTP to the coding contacts rather than di- 

